The present invention relates to a material testing system for applying force loads to a test specimen. More particularly, the present invention relates to material testing system that applies multiple force loads simultaneously.
The physical testing of materials by taking a test specimen and applying tension and/or compressive loads using an actuator is well known. Commonly, a single actuator is used, which if properly controlled can apply a single time varying load. However, the loading upon these materials when used in complex machinery is rarely from a single source. Typically, there exist multiple load sources each of which apply time varying loads of different frequencies.
Accordingly, testing machines have ben developed to apply multiple force loads simultaneously. United Kingdom Patent Application GB 2081457A discloses one such machine which includes a spring element interposed between two actuators, the first actuator being connected to the test specimen and the second actuator being connected to the test frame. As disclosed, the first actuator applies cyclical loads having a lower fundamental frequency and greater amplitude than the second actuator. However, this series connection orientation of the actuators and spring element requires that the second actuator must be capable of transferring the high amplitude loads of the first actuator.